In recent years, there has been a significant improvement in performance and reduction in size of a monitoring camera and an in-vehicle camera that use an image pick-up device such as a CCD image sensor or a CMOS image sensor and there has been a growing demand for an imaging lens system with a small F-value and excellent lens speed. It is generally known that when the F-value of the imaging lens system decreases, the field curvature and the lateral aberration increases and an imaging performance deteriorates.
Patent Literature 1 discloses an imaging lens system used for an in-vehicle camera, a monitoring camera or the like. The imaging lens system disclosed in Patent Literature 1 includes six spherical glass lenses.